Video: You have to strike while the iron is hot. You can't have too many irons in the fire. It has a nice ring to it. Go at something hammer and tongs. These are all idioms that have origins in blacksmithing, so Scott Wadsworth of Essential Craftsman decided to literally show us what all those idioms look like when performed in real life and explain how they are related to their meaning.
It's kind of fun to see the idioms as actions, instead of just phrases. You get to compare the actual difference between striking while the iron is hot versus striking while the iron has cooled off. When the metal is hot, it gets flattened in three strikes. When the metal is not hot, hammering it does nothing. The thinking behind the idiom, of course, is that the same amount of work can have a much greater effect when conditions are right.
Wadsworth illustrates more of those idioms in the video below.